Remember: LP must be preceded by a CT (or MRI) if there is any evidence of impairment of consciousness, focal neurological deficits or a prior seizure due to the risk of tonsillar herniation or coning.

Management

Bacterial meningitis is a medical emergency and requires immediate antibiotic therapy. Broad-spectrum antibiotics are indicated while lumbar puncture results are awaited.
Neonate: Ampicillin + third-generation cephalosporin or ampicillin + gentamicin.
One–three months old: Ampicillin + third-generation cephalosporin.
Infant and child: Ceftriaxone or cefotaxime.
Older child and adult: Ceftriaxone or cefotaxime + ampicillin (if Listeria suspected).
More than 50 years old or alcoholic: Third-generation cephalosporin + intravenous vancomycin.
Change to specific antibiotics once culture results are available and continue antibiotics for 14 days.
Dexamethasone reduces risk of deafness in children.

Remember: Meningitis is a medical emergency requiring urgent antibiotics, which should be commenced as soon as the disease is suspected, preferably after the CSF sample is obtained, provided this does not significantly delay treatment.

Complications

Arteritis, venous thrombosis, cerebral infarction; hydrocephalus; cranial nerve deficits; infected intracranial collections, including subdural empyema and cerebral abscess; ventriculitis; subdural effusions and seizure disorder.

Prognosis

Neonatal meningitis carries a mortality of up to 50%. Of the survivors, 50% have permanent sequelae. S. pneumoniae and N. meningitidis meningitis carry a mortality of up to 25% and 10%, respectively.

Differential Diagnoses (Table 21.1, Also See Table 4.2)

Table 21.1 Differential diagnoses with distinguishing features and points of note.

Clinical conditions	How to exclude it
Viral meningitis	Enterovirus, mumps and Herpes simplex are the principal causes. Look for signs of systemic viraemia. Lumbar puncture: lymphocytic pleocytosis (<300/mm³), normal glucose and normal to mildly elevated protein
TB meningitis	Consider other foci of tuberculous infection. Inflammation chronic, predominant in basal cisterns. Meningeal arteritis, cerebral infarction and hydrocephalus are frequent. Lumbar puncture: elevated opening pressure, lymphocyte pleocytosis (100–500 cells/mm³), elevated protein (100–200 mg/dL) and low glucose (<40 mg/dL). Cultures may not be positive for up to 8 weeks. PCR for tuberculous antigen may be useful
Fungal meningitis	Cryptococcus, candida and Aspergillus infections. Occur in immunocompromised hosts. Lumbar puncture findings as in TB meningitis. C. neoformans identified in India ink preparations of the cerebrospinal fluid, confirmed on positive latex agglutination test for cryptococcal polysaccharide antigen
Neoplastic meningitis	Associated with metastatic disease (leukaemia commonest in children; breast, lung and melanoma, in decreasing order, in adults). Lumbar puncture: elevated opening pressure, lymphocytic pleocytosis, low glucose and positive cytology for tumour in up to 80%. Postcontrast MRI shows leptomeningeal deposits, meningeal enhancement or hydrocephalus
Lyme disease	Meningoencephalitis, due to infection by Borrelia burgdorferi. Cranial or peripheral neuritis, particularly facial nerve involvement, erythema chronicum migrans, arthritis. Cerebrospinal fluid: lymphocytic pleocytosis (<3000/mm³), elevated protein and normal glucose. Definitive diagnosis by lyme serology testing.
Encephalitis	Symptoms of meningitis are associated with impairment of consciousness, seizures and focal deficits. Cerebrospinal fluid: characterised by mononuclear pleocytosis, elevated protein, normal glucose and occasionally red cells, positive Herpes simplex virus PCR. Imaging (CT and MRI) shows asymmetric temporal lobe involvement in Herpes simplex encephalitis. EEG shows periodic high-voltage sharp waves and slow-wave complexes at 2–3 s intervals in the temporal leads
Subdural empyema	MRI demonstrates focal or diffuse subdural collection, with enhancing margins, cortical oedema and mass effect, often with evidence of cortical venous infarction. LP is not indicated and is potentially dangerous
Cerebral abscess (Chapter 22)	CT and MRI show ring-enhancing lesion with surrounding cerebral oedema and mass effect. May be multiple. Diffusion restricted on diffusion-weighted image. Lumbar puncture is potentially dangerous. Remember Toxoplasmosis is a potential agent causing cerebral abscess in an immunocompromised patient, for example with AIDS

Note on CSF Shunt Infections

Meningitis/ventriculitis may follow insertion of a ventriculoperitoneal shunt, used to treat hydrocephalus. Infection may manifest in the postoperative period or in a delayed fashion weeks or even months later.
Clinical features of meningitis may coexist with those of raised intracranial pressure due to associated shunt blockage. Urgent discussion with regional neurosurgical unit is advised as shunt is likely to require removal in addition to treatment of CSF infection.

< div class='tao-gold-member'>

Only gold members can continue reading. Log In or Register to continue